RT-AC88U cannot update from 386.2_4 to 386.2_6 and pop-up error message "Invalid Firmware Upload"

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New Around Here
Hello everyone,

I trying to update my RT-AC88U but I cannot update from 386.2_4 to 386.2_6. :(

RT-AC88U update Error.jpg


New Around Here
I just ran into this issue as well running the latest stock firmware. It seems that the latest Asus RT-AC88U firmware changed to include certificate checks.

I'm not sure how to get around it when already running Asus/Merlin but here's what I did to get around the error when going from Stock to Asus/Merlin:

1) Ensure that Auto Upgrade is off (something added recently to the stock firmware as well)
2) Download the .385 firmware from the Asus site
3) Install that via Manual Firmware Upload
4) Once it's rebooted, log on and then install the latest Asus/Merlin
5) Bingo

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